Water Activity

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Price of the test:

$45 per analysis

Acceptable Matrices:

Nearly all foods and food products

Unacceptable Matrices:

Samples containing high levels of propylene glycol

Limit of Detection:

0.250 aw units (lower limit)

Sample Size Requirements:

10 grams


Water Activity Meter

Reportable Units:

aw Units
(Water activity, aw is the ratio of vapor pressure of the water in the sample to the vapor pressure of pure water at the same temperature)

Turn Around Time:

10 business days

Is Rush Available?


Method Reference:

AOAC 978.18

Method Description:

This method is a measurement relating to the free, unbound water present in food and food products.

The atmosphere of a special sampling cell is evacuated, repressurized and then measured manometrically. The results are correlated to water activity in the sample

Additional Information:

Water activity has little, if any, relationship to the total moisture content of the food. Water activity does provide a means of assessing the storability and bacterial susceptibility of shelf-stable foods. It is known that microorganisms cannot survive below certain aw levels, the level being dependent upon the type of microorganism: Botuli at <0.93; Bacteria at <0.86; Yeast cells at <0.78 and Mold spores at <0.65.